Total joint replacement prostheses typically include a specially designed jig or fixture to enable a surgeon to make accurate and precise bone resections in and around the joint being prepared to accept the prosthesis. The ultimate goal with any total joint prosthesis is to approximate the function and structure of the natural, healthy structures that the prosthesis is replacing. Should the prosthesis not be properly attached to the joint or not properly aligned, discomfort to the patient, gait problems, or degradation of the prosthesis may result.
Many surgical procedures employ the use of intra-operative fluoroscopy to check the alignment of the instrumentation relative to the patient's anatomy, such as the intramedullary cavities that are to be prepared to receive the joint replacement prosthesis; however, the use of intra-operative fluoroscopy may have drawbacks. One such drawback is that the use of fluoroscopy to check the alignment of intramedullary cavities formed during surgery may increase the overall length of the surgical procedure as time is taken to acquire and evaluate the fluoroscopic images. Long surgery times may lead to increased tourniquet time for the patient and may therefore increase recovery time.
Another drawback of fluoroscopy is exposing the patient and others in the operating room to the ionized radiation. For example, the U.S. Food and Drug Administration (“FDA”) has issued several articles and public health advisories concerning the use of the fluoroscopy during surgical procedures. Consequently, even though steps are taken to protect the patient and other from the ionized radiation, it is virtually impossible to eliminate all risk associated with the ionized radiation.
Thus, it is desirable to overcome the limitations of the prior art and provide an efficient fluoroscopy check of the alignment of prostheses with or without the assistance of a preoperative plan or assessment.
Further, achieving a proper vantage point is important when assessing an internal anatomic feature with an external radio-opaque indicator. For example, if an object is not properly aligned with a respective imaging system, projection of the external radio-opaque indicator may provide an improper assessment. This is known as parallax. Parallax can also cause distortion of a projected image due to the non-parallel rays from the x-ray source. Therefore, establishing the proper view of the subject matter herein is key, and embodiments disclosed herein describe a feature to assist in obtaining such a proper view.
For patient-specific surgical alignment guides, surgical planning for implant sizing and alignment may be performed pre-operatively based on a computer tomography (CT), magnetic resonance imaging (MRI) or other three dimensional (3D) medical imaging dataset, usually in a 3D computer aided design (CAD) environment. Based on the planned location and alignment of the respective implants, the surgical alignment guide may be designed to replicate the planned implant alignment in concert with the other surgical preparation instruments by fitting over the patient's bone and/or cartilage in one specific position based on the topography of the patient's anatomy. As an additional intra-operative check a fluoro image may be useful in confirming that the location of the alignment guide has been achieved to the surgeon's satisfaction. Such an ability to check the alignment of the guide early in the surgical procedure, prior to fully committing to the placement of the alignment guide, may reduce the risk of improperly preparing the bone and give the surgeon an opportunity to find a location and alignment of the guide that meets his expectations.